No wi-fi calling on t-mobile since installing spitz AX GL-X3000

Routers Cellular, USB modems
15

I’m sorry for your loss, and I’m glad everything worked out for you during that difficult time.

I wanted to share an update regarding my efforts to enable wifi-calling on the 5G SA network. After some extensive tinkering, I’ve managed to find a workaround that is working for now. Let me explain the steps I took:

  1. First, I adjusted my APN Configuration to Band Lock, ensuring that only 5G SA is used. This preference for a pure 5G network with 5G Core, rather than 5G NSA which utilizes 4G LTE, was important to me, even though 5G NSA assigns proper private IP4 addresses.

  2. Additionally, I set the IP6 configuration to NAT6, which allowed me to obtain public IP6 addresses on all my devices and IP4 addresses using T-Mobile’s CGNAT and 464XLAT CLAT.

  3. One of the challenges I encountered was that users on the 5G SA network were all assigned the same IP address (192.0.0.2) and gateway (192.0.0.1). Despite being able to ping the wifi calling servers, my iPhone still refused to connect.

  4. To address this issue, I set up WireGuard with custom rules enabled. I specifically configured the following IP ranges with a metric of 0 and a scope set to link: 208.54.0.0/16, 66.94.0.0/19, and 206.29.177.36/32. This configuration ensures that only these IP blocks traverse the VPN.

  5. Since implementing these changes, all my traffic has been successfully traversing T-Mobile’s IP4 and IP6 network without any issues. Interestingly, using NAT6 and 5G SA has even allowed me to use my Xbox and multiplayer games without the need for a VPN.

  6. I also confirmed with ipleak.net that all T-Mobile addresses and DNS servers are reachable. As a result, I can now make and receive texts and calls on wifi-calling even when my phone is in airplane mode.

While this workaround has proven effective, I believe there is still room for improvement. It may be worth exploring options such as proper configuration of 464XLAT on the router or potentially utilizing NAT hole punching to achieve a more streamlined wifi-calling SIP setup without the need for a VPN and custom rules.

After implementing these modifications, I have achieved download speeds of 485mbps or higher and upload speeds of 85mbps or higher, with a low ping of 9. In comparison, the 5G NSA network provided download speeds of around 350mbps or higher, upload speeds of 35mbps or higher, but with a higher ping of 62. These results highlight the improved performance and responsiveness of the 5G SA network with the implemented changes.

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